Revert "Rework fix for PR19460 - Use explicit bool as an extension instead."

This reverts commit 3a1b90a866b6d5d62a5f37fbfb3a1ee36cc70dd1.

llvm-svn: 291921

1 files changed, 17 insertions, 0 deletions

diff --git a/libcxx/include/ios b/libcxx/include/ios
index efee39fb533..b05ee4c785a 100644
--- a/libcxx/include/ios
+++ b/libcxx/include/ios
@@ -572,6 +572,13 @@ ios_base::exceptions(iostate __iostate)
     clear(__rdstate_);
 }
 
+#if defined(_LIBCPP_CXX03_LANG)
+struct _LIBCPP_TYPE_VIS_ONLY __cxx03_bool {
+  typedef void (__cxx03_bool::*__bool_type)();
+  void __true_value() {}
+};
+#endif
+
 template <class _CharT, class _Traits>
 class _LIBCPP_TEMPLATE_VIS basic_ios
     : public ios_base
@@ -585,8 +592,18 @@ public:
     typedef typename traits_type::pos_type pos_type;
     typedef typename traits_type::off_type off_type;
 
+  // __true_value will generate undefined references when linking unless
+  // we give it internal linkage.
+
+#if defined(_LIBCPP_CXX03_LANG)
+    _LIBCPP_ALWAYS_INLINE
+    operator __cxx03_bool::__bool_type() const {
+        return !fail() ? &__cxx03_bool::__true_value : nullptr;
+    }
+#else
     _LIBCPP_ALWAYS_INLINE
     _LIBCPP_EXPLICIT operator bool() const {return !fail();}
+#endif
 
     _LIBCPP_ALWAYS_INLINE bool operator!() const    {return  fail();}
     _LIBCPP_ALWAYS_INLINE iostate rdstate() const   {return ios_base::rdstate();}